Closures having end panels incorporating vacuum indicating buttons are used extensively for the food industry because they are effective quick-detection means that lets one know some very important conditions about the container. When the container is properly sealed and a vacuum exists therein, the button is in a "down" position while if the container has been opened and the closure reapplied, or the vacuum within the container otherwise lost, the button will be in its "up" position.
While closures having vacuum actuated buttons are predominately in use, there has been more recently developed closures with buttons which are mechanically actuated so as to move from an as formed "down" position to an upwardly projecting "up" position when the closure is properly applied to a container.
In both end panel displacement systems, there is a need for an irreversible type of tamper indicating system for use in conjunction with closures having deflectable end panel areas, such as buttons.